1. Field of the Invention
The present invention relates to an electrically driven turbocharger device installed into an internal combustion engine which is mounted on an automobile and the like, wherein the decreasing of the compressor capacity as well as the increase of the delivery air temperature can be constrained, while the inverter and the motor which are installed in the electrically driven turbocharger device can be cooled by the air inhaled into the electrically driven turbocharger device.
2. Background of the Invention
In the conventional internal combustion engine used for an automobile and the like, the engine is often combined with an exhaust gas turbocharger in which a turbine is driven at high speed by the exhaust gas emitted from the engine and the turbine drives a compressor via a common shaft which the turbine possesses with the compressor. Thus, in order to drive the turbocharger, the exhaust gas emitted from the internal combustion engine is necessary; however, it is difficult for the exhaust gas to quickly drive the turbocharger in starting the engine or in quickly accelerating the engine. Hence, in the electrically driven turbocharger device, the rotation of the turbocharger is performed by an electric motor or by the assistance of the electric motor. Patent Reference 1 discloses an example of the electrically driven turbocharger device. Based on FIG. 6, the electric turbocharger disclosed in Patent Reference 1 is now explained below.
In FIG. 8, an electrically driven turbocharger device 102 which is installed in an intake air flow passage 101 of an engine 100 includes, but not limited to:
a compressor 104 provided so as to face the intake air flow passage 101; an electric motor 106 driving the compressor 104;
a control device 108 controlling the electric motor 106;
a turbocharged air rate adjusting device 110 which sends an order for the turbocharged air flow rate to the a control device 108, turbocharged air rate adjusting device 110 including, but not limited to, a steering lever which a driver manually manipulates;
an indication device 112 which indicates the turbocharged air flow rate, the indication device 112 including, but not limited to, an instrument panel (not shown) placed in front of the driver seat; and
a power source 114 comprising including, but not limited to, a vehicle mounted battery and an alternator.
The control device 108 is provided with a driving device section 116 driving the electric motor 106, and a control order section 118 controlling the driving device section 116 in response to the turbocharged air flow rate which is set up by the driver. The control device 108 is provided with, for instance, a built-in inverter configured with a switching element such as a FET. By means of the inverter, the electric power from the power source 114 is transformed into AC electricity; and, the rotation speed of the electric motor 106 is controlled by arbitrarily changing the electricity voltage and the electricity frequency.
The electricity storage device such as a battery which the power source 114 configures is of a comparatively low voltage type; thus, heavy-current streams in the inverter and generates a large amount of heat in the inverter. Further, the rotation speed of the electric motor 106 is high and a large amount of heat is generated. Hence, it becomes necessary to cool the inverter or the electric motor.
Patent Reference 2 discloses a cooling device which cools the inverter or the electric motor in the electrically driven turbocharger device. Based on FIG. 9, the cooling device disclosed in Patent Reference 1 is now explained below.
In FIG. 9, an intake air ‘a’ is inhaled from an air inlet for inhaling the air for the compressor 202 provided in the intake air flow passage 200; the air is delivered to an engine (not shown) from the compressor. The intake air flow passage 200 is configured with three branch line passages which are branched at the air inlet 204 in three ways. In other words, a series flow passage 210 starts from the air inlet 204 and reaches the inlet of the compressor, passing by heat producing parts of an inverter 206 and an electric motor 208. A second series flow passage 212 starts from the air inlet 204 and reaches the heat producing part of the electric motor 208, bypassing the inverter 206. And, the bypass flow passage 214 starts from the air inlet 204 and is connected to the an intake air flow passage 216 on the air inlet side of the compressor 202, bypassing the inverter 206 and the electric motor 208.
In addition to these three flow passages, a bypass flow passage 218 is provided so that the bypass flow passage starts from the air inlet 204 and reaches the engine inlet side of the compressor, bypassing the inverter 206, the electric motor 208 and the compressor 202. At the branch point from which the second series flow passage 212 starts, a movable valve 220 is provided; at the branch point of the bypass flow passage 214, a movable valve 222 is provided; and, at the branch point of the bypass flow passage 218, a movable valve 224 is provided. Incidentally, the bypass flow passage is used in a case where the compressor 202 is stopped; accordingly, the movable valve 224 is usually closed.
As shown in FIG. 8, when the compressor 202 is not operated, the second series flow passage 212 and the bypass flow passage 214 are shut by closing the movable valves 220 and 222. When the compressor 202 is started, the rotation speed of the compressor reaches at an idling speed of several thousands to ten thousand rpm; thereby, all the intake air ‘a’ inhaled through the air inlet 204 is supplied to the series flow passage 210; the intake air ‘a’ cools the inverter 206 and the electric motor 208.
As shown in FIG. 8, when the compressor 202 is placed under an operation condition, the rotation speed of the compressor reaches a high speed of several tens-thousands rpm to hundred-thousand and several tens-thousands rpm. Thus, the intake air flow rate increases; consequently, if all the intake air ‘a’ is supplied to the series flow passage 210, the pressure loss in the intake air flow becomes greater. Hence, the three flow passages, namely, the series flow passage 210, the bypass flow passages 214 and 218 are opened, and the intake air ‘a’ is supplied to the series flow passage 210 so that the flow speed reaches a sufficient speed which is necessary for the intake air flow to cool the inverter 206 and the electric motor 208.